The present invention relates to a method and apparatus for forming silica network particles in water using magnetic treatment and the gradual adsorption of carbon dioxide from air, and also relates to an aqueous composition that includes the silica network particles and can be used to hydrate body parts such as skin.
The use of magnetic fields to alter the course of chemical reactions in water has been reported in the scientific literature for some time. For instance, in xe2x80x9cExperimental Evidence for Effects of Magnetic Fields on Moving Water,xe2x80x9d IEEE Transactions on Magnetics, Vol. Mag-21, No. 5, September 1985, pages 2059-2061, Kronenberg reported that passage of a water layer in which a calcium carbonate precipitate was forming altered the crystal form (growth habit) of the precipitate; and in U.S. Pat. No. 4,888,113, there is disclosed a device including bar magnets placed on either side of a pipe, which prevents the formation of carbonate scale in the pipes.
It is also reported in the patent literature that an aqueous colloidal silica can be formed from soluble silicates by repeated passage of the silicate solution through an appropriately structured magnetic field. For example, U.S. Pat. Nos. 5,658,573, 5,607,667, 5,599,531 and 5,537,363 disclose a method and an apparatus for generating a silicate colloid from a highly alkaline and nonstoichiometric solution of sodium silicate using a quadrupole magnetic field. It is reported that the method and apparatus produce particles from 10 to 100 angstroms in size. These patents also report that the silicate colloid produced using the method and apparatus can be used as a hydrating agent in body care and hair care compositions.
Generally, hydrating agents are incorporated into skin care products in order to enable water to penetrate into skin. The skin consists of two layers: the epidermis, the outer layer, and the dermis, the inner layer. The epidermis is a stratified, squamous epithelial layer whose cells undergo a process of division and differentiation. The outermost portion of the epidermis is the keratinized stratum corneum. The keratinization provides mechanical protection and is also a water barrier. Therefore, it not only helps keep the internal milieu constant and prevents water loss, but also prevents easy access to the deeper layers by environmental products. This physical attribute thus makes it difficult to hydrate the inner layer of the skin when it becomes dry. Accordingly, there have been efforts to prepare a hydrating agent that when incorporated into a skin care composition allows the composition to hydrate the skin faster and more easily than bulk water.
Although it is reported in U.S. Pat. Nos. 5,658,573, 5,607,667, 5,599,531 and 5,537,363 that the colloidal silica prepared by the disclosed methods satisfies the need for a hydrating agent that will enable water to penetrate skin, it is believed the colloidal silica disclosed in these patents does not provide an optimum solution to the problem of inadequate hydrating action in skin care products. Specifically, the particle size distribution and the particle structure of the colloidal silica in the aqueous composition in U.S. Pat. Nos. 5,658,573, 5,607,667, 5,599,531 and 5,537,363 significantly limit: (1) the water retention and exchange characteristics of the colloid; (2) the extent of interaction of absorbed water on the colloidal silica; (3) the interaction of an aqueous composition including the colloid with a hydrophobic substrate; and (4) the wetting properties of an aqueous composition including the colloid on a hydrophobic substrate.
Accordingly, there is a need for an silica composition with a particle size distribution and particle structure that improves the water retention and exchange characteristics of an aqueous composition including the silica composition. In addition, there is a need for an aqueous silica composition that has improved wetting characteristics when interacting with a hydrophobic substrate.
The foregoing needs are satisfied by aqueous silica network particles with unusual water retention and exchange properties. The silica network particles are generated in water by a method in which an aqueous sodium silicate solution is subjected to vigorous agitation in air, followed by periods of circulation through magnetic fields of alternating direction and further periodic agitation exposed to the air. The incorporation of carbon dioxide from the air occurs in both stages of agitation in this process. The result, at the end of the method, is aqueous silica particles with unique network morphology. The term xe2x80x9cnetworkxe2x80x9d as used herein describes a morphology wherein bridging particles form chains between main particles. This network morphology can also be described as a three dimensional mesh-like structure. With this network morphology, fluid regions are contained within the network. In one version of the invention, the aqueous silica network particles have a structure comprising bridging particles that form chains between adjacent main particles, wherein the main particles have a particle size greater than the bridging particles. An aqueous composition having the silica network particles has a lower interaction energy with hydrophobic materials than bulk water, and when added to a typical skin care preparation, enhances the exchange of water with the layers of skin.
Without intending to be bound by theory, it is believed that when the silica network particles are present in an aqueous composition, the network of each particle surrounds and encloses layers of bound water with a structure appreciably different from that of bulk water. It is believed that the alternating magnetic field used in generating the silica network particles serves to change the rate at which stable aggregates of water molecules form around other molecules or ions, which in turn alters the aggregation kinetics of the silica to produce the network particle morphology. In the normal polymerization of silicate solutions, a variety of particle sizes are formed, but a form of Ostwald ripening predominates wherein bigger particles grow at the expense of smaller particles. In contrast, the silica in the present invention forms the aforementioned network particle structure. It is further believed that the unusual properties of the silica network particles of the present invention are due to the gradual lowering of pH as carbon dioxide is absorbed, favoring chain formation over particle growth, and the stabilization of water clathrate-like structures around molecular carbon dioxide that absorb on the surface of larger but not smaller particles favoring the formation of chains of smaller particles. The result is silica network particles in water with an unusual physical reactivity to liquid water.
An aqueous composition of the silica network particles can be beneficially used as a hydrating agent in a wide variety of body care compositions, such as shampoos, conditioners, styling gels, styling mists, hair coloring preparations, body lotions, face creams, skin creams, bath additives, pedicure and manicure applications, hand lotions, lip balms, mouthwashes, toothpaste, lipsticks, suntan lotions, and sunscreen lotions. The use of an aqueous composition including the silica network particles in facial cleansers, moisturizing creams, and facial mists provides a package for improvement of skin and mucus membrane moisture, tone, and youthful appearance.
It is therefore an object of the present invention to provide an aqueous composition including silica particles that have a particle size distribution and particle structure that improve the water retention and exchange characteristics of an aqueous composition including the silica particles.
It is another object of the present invention to provide an aqueous silica composition that has improved wetting characteristics when interacting with a hydrophobic substrate.
It is a further object of the present invention to provide a body care composition that has improved hydration characteristics when compared to known body care compositions.
It is still another object of the present invention to provide a method for forming an aqueous composition including silica particles that have a particle size distribution and particle structure that improve the water retention and exchange characteristics of an aqueous composition including the silica particles.
It is yet another object of the present invention to provide an apparatus for forming an aqueous composition including silica particles that have a particle size distribution and particle structure that improve the water retention and exchange characteristics of an aqueous composition including the silica particles.
These and other objects, advantages and aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention.